In Late Antiquity the city of Side had a much shorter, strategic line of defences built within its original line of Hellenic walls. These new defences incorporated the theatre as part of the defensive line. The triumphal arch attached to the theatre also became part of the defences and the arch's aperture was significantly reduced. The new defences were built primarily of spolia looted from derelict or abandoned buildings in and around the city. The clearest evidence of spolia use in the walls can be seen in the use of column drums usually included to add strength to the walls by tying the two outer faces together. The last image, in the background, behind the building covered in scaffolding (The temple of Tyche), shows the late antique part of the wall in front of the theatre.

Late Antique portion of the city walls on the south west edge of the Lower Agora on the acropolis. Much like many other Late Antique defences these fortifications are made up of significant amounts of spolia that was robbed from nearby dilapidated or ruined buildings. These walls were likely built as the city contracted in Late Antiquity.

The most northerly fortified section of the acropolis of Pergamum immediately north of the Temple of Trajan. Within this part of the fortifications lie several warehouses or arsenals believed to be for the storage of provisions, weapons and ammunition. Excavations have recovered significant numbers and varying sizes of stone shot for catapults.